Data transfer method for halting communication of data when a transfer gap is detected

ABSTRACT

A data transfer method via a packet oriented channel and a continuous channel in parallel between a mobile station and a base station, where the transfer via the continuous channel is interrupted whereby at least one transfer gap is formed.

Exemplary embodiments of the present invention relate to data transferor data transmission methods, that utilize the interdependencies betweencompressed mode and data transfer, especially between compressed modeand packet oriented data transfer e.g. in UMTS (Universal MobileTelecommunications System) via HSDPA (High Speed Downlink PacketAccess), cf. [3]. Compressed mode is applied under an embodiment ifinter-frequency measurements, e.g. for handover procedures or OTDmeasurements, are performed.

BACKGROUND

Terminal or user equipment in a communications system may performmeasurements on frequencies different from its actual sending/receivingfrequency in order to observe measurements from devices such as basestations or to perform OTD (Observed Time Difference) measurements.During this time (transfer gap) no data transfer takes place. Tomaintain an average data transfer rate, the data rate outside of thetransfer gap is increased in certain time frames. The operational modein these time frames is referred to as compressed mode. This compressedmode influences the data transfer, and creates interdependencies amongvarious data.

A base station is typically defined as a central unit in a cellularcommunications network, that serves terminals or user equipments withina cell of the communications network. Typically, it comprises at least asending/receiving unit. In UMTS it is often referred to as node B.

This can be described by using an example regarding a UMTS System:

During a connection that is established between a communication deviceor user equipment (UE) and a base station (BS or Node B), the userequipment may also observe other base stations in order to find out thebase station the optimum connection can be installed to.

For observing another base station, the user equipment has to tune in onfrequencies distinct from its actual sending/receiving frequencies. Thusduring the time the user equipment is observing other frequencies, nodata is being transmitted or received, at least if the user equipmenthas only one synthesizer and/or only one RF-part (RF: Radio Frequency).

However, the user of the user equipment should not notice under normalworking operation, that the data transfer has been disrupted in order tocreate transfer gaps for the so called “inter-frequency measurements” bywhich frequencies distinct from the actual sending/receiving frequencyor frequencies are observed. In the framework of the UMTSstandardization, this item is dealt with in [1].

To maintain a constant average data rate in the presence of transfergaps, the net data transfer rate is increased before and after thetransfer gaps. “Net data” in this context refers to data actuallycarrying information. A predetermined overhead is added to the net datato ensure that the data can be decoded correctly at the receiver, evenif the transmission has not been ideal, i.e. experiences somedegradation. The overall data is referred to as gross data, wherein theoverhead of data may consist of parity bits originating from channelcoding. Data transfer may be either the transmission or the reception ofdata or both.

An illustration of a transfer disrupted by a transfer gap TG, e.g. atransmission gap, is shown in FIG. 1, which is taken from [1]: Thetransmit power is depicted versus time, wherein the latter is segmentedin frames F as time intervals, each frame itself contains several timeslots. The frames during which the user equipment listens to anotherbase station and thus cannot be transferring data continuously arereferred to as compressed frames, as the transfer rate has to beincreased in some timeslots in this frame to achieve an average ratesimilar to normal frames, that is when the compressed mode is off.

The frames, in which the data are transferred compressed, are referredto as compressed frames, and the respective operating mode as compressedmode.

In compressed frames, TGL (transmission gap length) slots from a firstslot N_(first) to a last slot N_(last) are not used for transmission ofdata. As illustrated in FIG. 1, the instantaneous transmit power P,which is depicted versus time t, is increased in the compressed frameF_(c), before and after the transmission gap TG with the length TGL inorder to keep the quality (the BER (Bit Error Rate) or the FER (FrameError Rate)) unaffected by the reduced processing gain. F denotes thelength of a normal frame. By “reduced processing gain” it is meant thatthe data is encoded less safe than during “normal transmission”. Theamount of power increase depends on the actually used transmission timereduction method (see [1], subclause 4.4.3).

In FIG. 2 an ordinary transmission sequence can be seen, which is usedto explain the terms demodulation, coding etc.

The signal may be generated at the source or transmitter TX. In asubsequent analog to digital converter A/D the signal is digitized, thusthe smallest information carrying unit is one bit. Digitizing includesthe steps of sampling and quantizing the signal. Then various codingsteps in the encoder C are performed: source coding is performed to getrid of redundancies in the signal or digitized data are used directly(which means no A/D converting or source coding etc needs to be done);channel coding is applied to protect the bits. After coding the signalis spread. At this point the smallest information carrying unit is achip. Due to spreading the chip rate for a transmission is typicallyconsiderably higher than the bit rate.

At the digital modulator DM the data is ‘translated’ into symbols thatdiffer for the various modulation and coding schemes. The higher amodulation the higher the number of bits that are translated into asymbol.

Next the data being transferred may be subject to influences from noiseand interference that can have an impact on the data. For example aprevious symbol (1,1) at the digital demodulator might be changed to(0.7,0.9). Hence, the transfer is referred to via an analogous channelAC. At the receiving side the corresponding processes of demodulation atthe digital demodulator DD and the decoding at the Decoder D and thedigital to analog conversion at the D/A converter are taking place.

Generally speaking, in compressed mode the transmit power is increasedto ensure a safe transmission of the less safe encoded data: By codingthe data less, with the same gross data transfer rate a higher net datatransfer rate can be achieved. The data bits are preferably punctuatedmore than in the frames before or the coding of the data bits has beenperformed with a lower spreading factor. The compressed mode thereforeentails rather complex calculations how the gross data are modified

-   -   depending on the gap length    -   and on the current data transfer rate    -   and on the duration of the compressed mode (cf. FIG. 1, the time        required for the time slots with the higher transmitting power)    -   and in how this modification is realized, e.g. by using a        different modulation scheme    -   a different spreading factor puncturing of data, i.e. cutting        out individual or group of bits.

It is decided by the network which frames are compressed. When incompressed mode, compressed frames can occur periodically or requestedon demand. The rate and type of compressed frames is variable anddepends on the environment and the measurement requirements. InOSI-layers above the physical layer the knowledge of the scheduling ofthe compressed frames is existent, thus the above mentioned calculationsfor the compressed mode can be done. As a further variant for therealization of compressed frames, it is known that higher layers canalso restrict the data rate during frames which will undergo compressionon the physical layer, thus making the operation in compressed mode morereliable because less excessive rate matching will be necessary for thecompressed frames due to the lower data-rate.

Furthermore, transmission gaps can be placed at different positions,depending on factors such as interfrequency power measurement,acquisition of control channel of another system or carrier and handoveroperation, cf. [1], section 4.4.4. For the so called single framemethod, the transmission gap is located within the compressed frame. Theexact position depends on the length of the transmission gap TGL(transmission gap length). For the double frame method the transmissiongap is overlaps two neighbored frames. In the example of FIG. 3 a(discussed in greater detail below), the single frame method is shown,in FIG. 3 b an example for the double frame method.

For example, this type of compressed mode is applied in UMTS (UniversalMobile Telecommunications System) to the DPDCH (Dedicated Physical DataChannel), across which data are transferred by circuit switching. Asexplained above, the methods for compressing the frames require rathercomplex calculations.

Furthermore, packet switched transfer modes, which may be operated inparallel to the circuit switched modes or continuous channels via whichdata, such as speech can be transferred, are affected by thetransmission gaps TG. This will be detailed below: In a packet switchedtransfer mode, the data is segmented into packets. Each packet istransferred individually. The quality of the reception is decided onbasis of various data operations such as demodulation or decoding (cf.FIG. 2). The receiver sends back a receipt of the reception, e.g. an‘ACK’ (Acknowledge) or a ‘NACK’ (Not acknowledge) depending whether ithas recognized a packet as been received correctly or not. A channelwith packet switched transfer mode such as in UTMS, the HS-DSCH (HighSpeed Downlink Shared Channel) is mapped to the physical channelHS-PDSCH. An overview of this technique is provided in [3].

The HSDPA data channel may be viewed as an enhancement of the existingUMTS.downlink shared-channel (DSCH). HSDPA allows to code multiplexdifferent users or mobile stations with spreading factor of up to 16codes. The primary multiple access, however, is in the time domain,where different users can be scheduled every transmission time interval(TTI), which corresponds to 3 UMTS slots, i.e., 2 ms. Also the number ofcodes allocated to one user can change from TTI to TTI. Depending on thesystem load and channel conditions, the base station or Node B adaptsmodulation and code rate for each user A predetermined combination ofcode rate and modulation is referred to as MCS (Modulation and CodingScheme) level. The MCS level may change every TTI. It is determined bythe base station based on feedback information or channel qualityinformation (CQI) from the user terminal or mobile station, which stemsfrom channel condition measurements. The channel quality information issent with a periodicity ranging from one to 80 TTIs.

To achieve the high data rates, modulation and coding schemes are usedwhich allow a high information bit rate per code. Therefore so called“higher modulation” techniques are used by which a symbol contains morethan 2 bits. One example is 16-CAM (Quadrature Amplitude Modulation).For these modulation techniques, the individual positions for a bitwithin a symbol are not equally protected. Therefore, there is theeffect of mapping important bits to well protected positions and lessimportant bits to less protected positions. This is referred to as bitpriority mapping and will be detailed below using an example from HSDPA.Furthermore, for channel coding so called “turbo codes” with rate R=⅓are used. The rate indicates the ratio of the total number of bits tothe number of load or systematic bits.

The HS-DSCH is shared among several users. The respective transfer ratefor each of the users is decided on basis of the individual channelquality. One of the multiple access possibilities is in the time domain,where different users can be scheduled every transmission time interval(TTI), which corresponds to three UMTS slots (UMTS: Universal MobileTelecommunication System), or 2 ms.

The transport channel HS-DSCH is mapped—as mentioned above—to thephysical channel HS-PDSCH (High Speed Physical Downlink Shared Channel),to which a compressed mode can be applied. For higher data rates, wherea single HS-PDSCH cannot carry the entire data rate, a set of HS-PDSCHchannels can be used, in this case all the HS-PDSCHs of the set aretransmitted simultaneously and they can be distinguished because theyuse different spreading codes. However, the invention as describedherein should not be affected whether one HS-PDSCH or a set is used.

In principle the above described compressed mode can be applied topacket switched data, too. Therefore calculations need to be done asdescribed in the references below (cf. [2]). However, a simpler processis desirable to make the calculations less complex.

SUMMARY OF THE INVENTION

An exemplary embodiment of the invention provides an easy solution tohandle the interdependencies between compressed mode and a packetswitched data transfer channel.

An exemplary embodiment of the invention provides a transmission method,where information is transmitted in packets, and where transmission orreception gaps are provided, whereby no transmission or reception isperformed during transmission or reception gaps.

The aforementioned embodiment includes a method and an arrangement whichare characterized by a data transfer method wherein data are transmittedin packets between a mobile station (MS) and a base station (BS),wherein no transmission or reception of data is performed duringtransmission or reception gaps, that are provided for a mobile stationto tune to other frequencies. The exemplary embodiment operatesregardless of whether data is transferred or transmitted in packetsoutside of transmission or reception gaps that can be used by the mobilestation to tune to other frequencies.

By a data transfer method according to an exemplary embodiment of theinvention, data is transferred between a mobile station and a basestation via a packet oriented channel and a continuous channel inparallel. Under this configuration, the transfer via the continuouschannel is interrupted such that at least one transfer gap is formed.

Under the aforementioned embodiment, after the reception of a datapacket no receipt, e.g. an ‘ACK’ or a ‘NACK’, is sent back by thereceiver after a first processing time. The first processing time isreferred to as ‘UE-processing time’ and denotes the time between the endof reception of a signal and the start of transmission of a successiveor subsequent signal, which may be an ACK or NACK signal as in the caseof the UMTS system. In UMTS 5 ms are allocated for the UE-processingtime. The timing structure of HSDPA is illustrated in FIG. 3, where alsothe length of 1 TTI can be seen, which corresponds to 2 ms in UMTS.

During a first processing time, the signal is prefereably demodulated,wherein a set of symbols is assigned to a set of incoming data, and toallot a probability to each symbol or bit, that the decision for asymbol or bit has been correct. By not sending a receipt during thetransmission gap the gap is maintained despite of the HSDPA transmissionand the gap can be used for the initially described observation of otherfrequencies.

Under another exemplary embodiment of the invention, a data packet isstored by the receiver to establish a first data set. A decoding isdone, when the data packet has been received repeatedly, thus at least asecond data set is provided. By a joint decoding of the data sets theperformance of the decoding process is improved in respect to decodinge.g. the first data set alone.

Under yet another embodiment of the invention, the receipt is sent backafter the processing time plus a certain delay. This also ensures, thatno receipt is transferred in the transmission gap.

Accordingly, a method is disclosed to restrict the scheduling of HSDPAtransmissions in order not to compromise compressed mode operation andstill sacrifice as little data throughput, especially HSDPA throughput,as possible.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its wide variety of potential embodiments will be morereadily understood through the following detailed description, withreference to the accompanying drawing in which:

FIG. 1 illustrates a scheme of a compressed mode transmission;

FIG. 2 is a block diagram of transmission process;

FIG. 3 illustrates possible positions of the time transmission interval,for a) the single frame method and for b) the double frame method;

FIG. 4 illustrates the throughput for HSDPA depending on the Modulationand coding scheme;

FIG. 5 is a timing structure of HSDPA uplink timing; and

FIG. 6 is a schematic diagram of a communications network showing datatransfer between a mobile station and a base station via a continuouschannel and a packet oriented channel, respectively, according to anexemplary embodiment of the invention.

DETAILED DESCRIPTION

The present disclosure will illustrate in greater detail variousapplications of the compressed mode and its implications on the HSDPAtransmission. Generally speaking, methods according to the inventionpropose to withhold sending any feedback during a transmission gap. Thisis done either by not sending any acknowledgement, e.g. an ACK or anNACK, that would be transmitted during a transmission gap, or by sendingit with a delay sufficient to postpone its transmission after thetransmission gap. As explained above, the feedback is normally used inpacket oriented transmission to acknowledge the receipt of atransmission (ACK) or the failure to receive a packet correctly.

As a result, the data packets whose acknowldegements are affected areeither being re-transmitted or not re-transmitted at all.

The above mentioned continuous data channel may be the DCH (DedicatedChannel) and the corresponding Dedicated Physical Data Channel andDedicated Physical Control Channel by which data, such as speech, can betransferred.

These considerations also apply to uplink and downlink compressed modescenarios as well. The following illustrations will differentiatebetween uplink and downlink compressed mode:

Restrictions on HSDPA Transmission Due to Downlink Compressed Mode

The restrictions that accompany (downlink) HSDPA transmission can bedescribed as follows: During the transfer gaps provided by compressedmode, the user equipment is free to tune to other frequencies andtherefore cannot receive any signals on its currently assignedfrequency.

In general, during the transfer gaps the user equipment may not receiveany signal. In other words, the base station may send signals during thetransfer gap, but signals are not necessarily received by the userequipment. Accordingly, under one embodiment the user equipment maydisregard specific details of the signal such as the offset of the DPCHagainst the HS-DSCH and HS-SCCH (High Speed Synchronisation ControlChannel) or the specific details of the compressed mode patterns or thedifferent frame structure types.

For any given offset and for given parameters of the compressed mode, acalculation is made as to whether HS-SCCH or HS-SDCH overlap with thetransfer gap. An overlap is typically given if any single chip of theHSDPA transmission would overlap with any single chip (see FIG. 2 andaccompanying text) of the transfer gap. Further more, because the HItransmission (HI:HS-DSCH Indicator) always fully overlaps thecorresponding HS-SCCH transmission (if the HI is transmitted at all, thesystem can also be designed without the HI), it is sufficient toconsider only the latter.

In another exemplary embodiment the base station does not transmit anydata. While it is preferable if the base station knows that the userequipment does not listen during the time in question, this does notnecessarily have to be the case. For example, if the transfer gap of thecompressed mode only partially overlaps with a HSDPA TTI, then it may bepossible for the user equipment to still receive parts of the TTI and,due to the error correcting coding which is applied, it might bepossible to decode the data packet also from this partial reception.This is in particular possible, if the packet was already aretransmission, in which case it might be possible to decode the packetbased on the received information of the earlier transmission(s) plusthat partial one. It may also be the case that successful decoding isnot possible due to the part of the TTI that is missed during the gap,however, the received part of the TTI, together with a subsequenttransmission may make it possible to decode the data.

Therefore, the user equipment receives at least part of the data even ifthe TTI (partly) overlaps with a transfer gap by compressed mode. Theuser equipment can then either perform a complete decoding or only storethese data in the user equipment soft buffer (how this is done will bedescribed in more detail in an other embodiment described herein). Inyet an other variant the user equipment may, at least for some transfergaps, decide that it does not need to interrupt communication as long asthe entire transfer gap, but only for a shorter time. This may bepossible if the actions that are scheduled for a particular transfer gapcan also be performed in this shorter time. This may be the case forexample, if the user equipment has a synthesiser that can be tuned tothe other frequencies more quickly than was assumed when therequirements were decided. Another possibility is that the actionscheduled for a particular transfer gap can inherently be done in ashorter time, e.g. a so called BSIC—verification on an other GSMfrequency (BSIC=Base Station Identification Code). This can be done in arather short time, but the exact position of this time within thetransfer gap may not be known at the base station when the transfer gapis being scheduled, so that a larger transfer gap is scheduled than willactually be necessary in the end.

Restrictions on HSDPA Transmission Due to Uplink Compressed Mode

The restrictions due to uplink compressed mode are somewhat different,because it is not the downlink HSDPA transmission that is causing thetrouble but the uplink sent receipt, e.g. the ACK/NACK (Acknowledge/Notacknowledge) transmission. During the transmission gaps for uplinkcompressed mode, the user equipment is not able (and therefore notrequested) to transmit anything, in particular not a receipt. However,this does not rule out the possibility for the base station, which inUMTS is also often called Node B, to transmit an associated downlinkHSDPA transmission before the transfer gap.

The only restriction a base station has to take into account is thefact, that it cannot expect the user equipment to transmit any receipt,e.g. either ACK or NACK, in response to this HSDPA transmission. As aconsequence, the base station will not get an information about whetherthe user equipment has correctly received the packet and will thereforehave to retransmit the packet in any case. Under this configuration, thethroughput can be increased, as the base station will not use a MCS(Modulation an Coding Scheme) where there is a fair chance that the userequipment will decode the initial transmission, but it will use a MCSwhere the second transmission has such a fair chance.

A modulation and coding scheme is also described, wherein the schemeidentifies which transmission method is being used for the packet, andfurther identifies the amount of redundancy that is used and isavailable for error correction purposes (coding), as well as themodulation scheme which describes how many bits are transmitted with asingle symbol. As an example, for QPSK (Quadrature Phase Shift Key) twobits are transmitted while for 16 QAM (Quadrature Amplitude Modulation)transmission 4 bits are transmitted. The code rate R describes how manyredundancies are being used, R is defined asR=Number of bits before of coding/Number of bits after coding

TABLE 1 Modulation and Coding Scheme (MCS) MCS code info bit levelmodulation rate R rate per code 5 16-QAM 3/4 720 kbps 4 1/2 480 kbps 3QPSK 3/4 360 kbps 2 1/2 240 kbps 1 1/4 120 kbps

The above table gives an example of a possible set of Modulation andCoding Schemes that can be used and FIG. 4 illustrates the throughputthat can be achieved depending on the channel quality for theseModulation and Coding Schemes.

The abscissa I_(or)/I_(oc) (described below) is the ratio of the totalpower spectral density of the downlink to one user terminal to the powerspectral density of the band limited noise and interference.

I_(or)/I_(oc) is defined as

$\frac{I_{or}}{I_{oc}} = {\frac{E_{b}}{N_{0}} \cdot \frac{R_{b}}{R_{c}} \cdot \frac{1}{g_{d}}}$

where E_(b)/N₀ is the bit energy to spectral noise density, R_(b) is thebit rate, and R_(c) is the chip rate. The factor g_(d) is fraction ofradiated power devoted to the HSDPA data channel. An total overhead of20% is assumed (e.g., for signalling channels and pilot channels whichare used to determine the influence of the transmission medium on thereceived signals by the user equipment) leading to g_(a)=0.8. Under thisconfiguration, the abscissa denotes basically the signal to noise ratio.

The steps in the throughput curves are achieved if the initialtransmission fails and a retransmission has to be done, which will makethe throughput drop in half for the second transmission, to a third forthe third transmission and so on. As can be seen from the graph, afterone retransmission a level 2 Modulation and Coding Scheme achieves athroughput of 129 kbps (kilo bits per second) after the secondtransmission, just as MCS level 1 for the first transmission, in asimilar range of the channel quality. In that range the same throughputcan be achieved with two transmissions of MCS level 2 as with a singletransmission of MCS level 1.

As a result, the initial transmission will have a rather low successprobability, which means the ACK/NACK signal that is ‘lost’, because itis not sent due to the uplink compressed mode transfer gap is mostlikely a NACK signal, thus rendering the information redundant.

It is noted that a scheduler (the control unit in the base station whichdecides which user equipment to serve during the next TTI and which MSCto use), is free to always use such an operating point or transfer mode,which also has the advantage of increased time diversity due tocombination of two transmissions at different times. The throughput of ahigher MCS with retransmission is very similar to the throughput of aMCS carrying half as much payload for an initial transmission. If thisscheme is employed, uplink compressed mode does not degrade thethroughput of a HSDPA session.

As mentioned previously, the base station will not schedule a HSDPAtransmission for a user equipment which is using compressed mode, ifpart of the HS-SCCH information or the corresponding HS-DSCH TTI (TTI:Transmission Time Interval) overlaps with a transfer gap of downlinkcompressed mode.

FIG. 5 illustrates how part of the HS-SCCH or the HS-DSCH can overlapwith a transfer or transmission gap:

A detailed timing diagram of the HSDPA channels in relation to otherUMTS channels is given in FIG. 5. FIG. 5 shows the timing offset betweenthe downlink HS-DSCH (High Speed Downlink Shared Channel) and the uplinkDPCCH (Dedicated Physical Control CHannel). The code-multiplexed uplinkHS-DPCCH starts m*256 chips after the start of the uplink DPCCH with mselected by the UE such that the ACK/NACK transmission (of duration 1timeslot) begins within the first 0-255 chips after 7.5 slots followingthe end of the received HS-DSCH. The UE processing time (indicated asτ_(UEP)) is therefore maintained at 7.5 slots (5.0 ms) as the offsetbetween DPCCH and HS-DPCCH varies. The ACK bit is sent on the first slotof the code multiplexed uplink HS-DPCCH. Every first slot on theHS-DPCCH, chosen according to the parameters above, are reserved forACK/NACK signaling (marked with A/NA in FIG. 5). The other two slots onthe HSDPCCH can be used for CQI transmission (marked with QI in FIG. 5).T_(slot) indicates the duration of one slot (i.e. 0.67 ms).

From FIG. 5 it can be seen, that the receipt, that is the ACK or theNACK is sent after the data. Therefore, the receipt can overlap with atransmission gap even if the actual data do not.

If a part of an ACK/NACK signal overlaps with a transfer gap of uplinkcompressed mode, the user equipment is not requested to transmit it.Instead, the user equipment may discontinuously transmit (DTX:discontinuous transmission) the affected timeslot on the uplinkHS-DPCCH. Furthermore the user equipment does not need to attempt todecode the transmitted packet, but is only requested to store the dataof the corresponding HS-DSCH TTI in the virtual user equipment buffer tobe able to combine them with data sent in subsequent TTIs.

The detailed operation of the scheduler in the base station can bevendor specific, and specific implementations of the scheduler can bedone by those versed in the art in accordance with the rules set forwardherein. All that needs to be specified, is the fact that the userequipment is not requested to transmit any receipt, e.g. a ACK/NACKsignal, that overlaps an uplink compressed mode transfer gap.Preferably, no overlap of even a single chip is allowed. As aconsequence, it will be invisible from the outside, whether the userequipment could correctly decode the HSDPA transmission and thereforethe user equipment does not even have to attempt to decode this packet,all it has to do is store the soft decision values in the virtual userequipment buffer where they will be combined with the next transmissionwhich will then be processed as usual, including transmission of anACK/NACK Signal.

Restrictions on QI Transmission Due to Uplink Compressed Mode

Similar restrictions due to uplink compressed mode as for the receipt(e.g. ACK/NACI (signal) affect also any other uplink HSDPA transmission,i.e. the Quality Indicator (QI) transmission.

The QI conveys information regarding the quality of the downlink channelas seen from the user equipment and is used by the base station todetect, which of the user equipments attached to a base station have agood reception and are therefore suited for HSDPA transmission.

Again, during the transfer gaps for uplink compressed mode, the userequipment is not able (and therefore not requested) to transmitanything, in particular not the QI transmission.

The QI transmission is intermittent or not continuous due to themeasurement feedback cycle, even if it is possible to request the userequipment to transmit a QI in every TTI as a special case.

Furthermore the base station has to process corrupted or undecodable QItransmissions, so no special actions or provisions are expected to benecessary for the QI transmission; it can simply be omitted if there isa collision with an uplink compressed mode transfer gap. Again, it ispreferable that not even a single chip of overlap is allowed.

As discussed previously, the user equipment is not requested to transmita Quality Indicator signalling, if a part of it overlaps with a transfergap of uplink compressed mode. Instead the user equipment may simply nottransmit anything during the affected timeslots on the uplink HS-DPCCH.This behaviour is also called DTX (Discontinuous Transmission).

Restrictions Due to Simultaneous Uplink and Downlink Compressed Mode

If both uplink and downlink compressed mode are activated at the sametime, or if multiple compressed mode patterns are activated, then therestrictions due to the individual transfer gaps exist in parallel. Thismeans a downlink or uplink transmission is only feasible, if it iscompatible with all the transfer gaps. Thus any receipt is not to besent in any transfer gap.

Further Aspects and Embodiments

In the above text, the disclosure illustrates how an uplink transmission(any receipt, e.g. ACK or QI) is not sent if it would overlap with atransmission gap.

Under yet a further exemplary embodiment, the affected transmission canalso be delayed until a time, when it is possible to do thetransmission. The delay can in principle take any value (e.g. thedelayed transmission could start immediately after the end of thetransfer gap). However, in order to ease the implementation, it ispreferable to delay the transmission by an integer number of timeslots.In case that more than one data packet has been transmitted during acompressed mode operation, that is more than one receipt is beingdelayed, the individual receipts are sent after the delay with aninterval of one timeslot instead of one TTI to catch up for the delayfaster than it would be the case with an interval of one or more TTIs.

Under yet a further exemplary embodiment of the invention, the delayedtransmission is not delayed by an integer number of timeslots, but by aninteger number of TTIs. This will ease the implementation at both theuser equipment and base station, because the delayed transmission willthen be received at a time when this type of transmission is anyhow due.Therefore the entire transmission respectively reception chain can beeasier implemented. Under this configuration, the entire system isdesigned and implemented so that it works optimum for the given delays,i.e. when the transmission is sent at the nominal time. Any furtherdelay will mean, that the action which is done in response to theACK/NACK or the QI will not be possible any more at the time without anydelay, but only at a later TTI. This action will accordingly be thescheduling decision on the next TTI, (i.e. which user equipment totransmit user data, which modulation and coding scheme to use andwhether to transmit a new packet or to repeat an old one). If theACK/NACK command is delayed by an integer number of TTIs, then theaforementioned response can also only be sent an integer number of TTIslater. If the delay is however less, i.e. an integer number of TTIsminus a fraction of a TTI, then the response can not be sent one entireTTI earlier, because the ACK/NACK came after the ‘deadline’ for thatTTI. In other words, trying to optimize the delay of a transmission ofan ACK/NACK (likewise for the QI which also influences subsequenttransmissions) by a fraction of a TTI is not desirable. Thus theimplementation of an integer of the number of TTIs is preferred.

Integer delays of the number of TTIs are used particularly if there is asimultaneous transfer gap in both uplink and downlink compressed mode,due to the backlog of the outstanding ACK/NACK signals which were builtup before the transfer gap could be finished after the transfer gap andbefore new ACK/NACK signals associated with HSDPA transmissions afterthe transfer gap have to be transmitted. The reason for this is that theHSDAP downlink transmission is longer than the ACK/NACK transmission,therefore the transfer gap blocks at least as many downlinktransmissions as ACK/NACK transmissions. However, in uplink onlycompressed mode (i.e. if there are gaps only in the uplink direction),this is not the case because no downlink frames are blocked. In order toavoid a backlog the ACK/NACK signal is not transmitted or,alternatively, the ACK/NACK signal is transmitted with a delay which isnot necessarily a multiple of a TTI. It is preferable to select amultiple of a timeslot. For reasons similar to those detailed above, itwould not be advantageous to select a delay which is not a multiple of atimeslot: None of the transmitted ACK/NACK signals would be receivedearlier than a fraction of a timeslot earlier compared to the slotaligned case.

In yet another exemplary embodiment, the delay can be set to be amultiple of slots which are not a multiple of a TTI at the same time.Under this configuration, delayed ACK/NACK transmissions that block thetimeslots which are allocated for current ACK/NACK transmissions can beavoided.

In yet another exemplary embodiment, only every second TTI can be usedfor transmission of delayed ACK/NACK signals, together with a newACK/NACK signal which needs not to be delayed, leaving two timeslots ofevery other frame available for QI transmission.

In yet another exemplary embodiment, a first delayed ACK/NACKtransmission (or multiple transmissions) are transmitted after thetransfer gap, subsequently followed by QI transmission, particularly ifa QI transmission would also have been scheduled during the transfer gapor during a delayed ACK/NACK signal.

In yet another exemplary embodiment, ACK/NACK and/or QI transmissionsare sent after the transfer gap, preferably at a time when otherACK/NACK signals or QI transmissions would be scheduled. In this casethese latter transmissions are also delayed, until they can be sent.

In yet another exemplary embodiment, ACK/NACK transmission isprioritised over QI transmission, i.e. if both an ACK/NACK signal ispending and a QI transmission the latter is further delayed and thepending ACK/NACK is transmitted before of the QI transmission.

In yet another exemplary embodiment, only a single QI transmission issent if a QI transmission has been delayed until the nominaltransmission time of a later QI transmission. Instead of transmittingtwo or more QI transmissions one after the other, it may be sufficientto send only one QI. Transmitting two QIs in short succession in thiscase is redundant, because the channel quality will not have changedsignificantly during such a short time.

In yet another exemplary embodiment, a QI transmission which cannot besent at its nominal time due to a compressed mode transfer gap isdelayed until a timeslot also allocated for QI transmission. It shouldbe noted that normally no QI may be sent during this particular timeslotbecause QI transmission is only done intermittently). Consequently, theQI transmission is delayed by an integer number of TTIs rather than aninteger number of timeslots.

Generally speaking, the following variations may be implements orcombined:

-   -   a) the delay is such, that the receipt is sent immediately after        the transfer gap.    -   b) the delay has the length of an integer number of time slots.    -   c) the delay has the length of an integer number of transmission        time intervals (TTI).

The present disclosure generally relates to HSDPA and compressed mode,however, as will be apparent to those skilled in the art, the sameprinciples can easily be applied to other systems or scenarios, where apacket communication is established, but some time intervals are notavailable for uplink or downlink communication due to constraints fromother aspects of the system. Such constraints can come from an othercommunication e.g. a circuit switched connection which runs in parallel.It can also be another system, which runs in parallel and isincompatible due to some reasons with the packet transfer and thereforecauses some time intervals not to be available for the packet transfer.Such other system can be another communication system, which competesfor some limited resources e.g. a receiver or causes mutualinterference. It can also be a completely different action, whichcompetes for e.g. energy sources or computing resources or otherresources.

For example, in FIG. 6 the transmission of data in a communicationssystem or network according to the UMTS standard comprises a terminal ormobile station MS and a base station BS. With the introduction of theHSDPA transmission, the data transmission, via a packet oriented channeland a continuous channel, are in parallel. Both channels have to provideor to establish transmission gaps during which the user equipment tunesto other frequencies. For a packet oriented channel, the followingaspects can be considered

-   -   a) No transmitting of packets during the transmission gaps    -   b) Receipts, e.g. ACKs or NACKs that are sent during the        transmission gaps will not be received. Therefor, the further        packet transfer has to be carried out without knowledge of that        receipt.

Further Aspects of the Invention in Respect of the UMTS Standardization:

During compressed frames (or gaps) on the DCH (Dedicated Channel) thereis no HS-DSCH (High Speed Downlink Shared Channel) activity for the UE(User Equipment), including signalling in DL/UL(Downlink/Uplink. (Note:Compressed mode is applied on DCH only).

The embodiments described below serve to restrict the scheduling ofHSDPA transmissions in order not to compromise compressed mode operationand still sacrifice as little HSDPA throughput as possible. At the sametime a compact formulation to be used in the Technical Report [5] andthe working change requests (CR) for the specifications 25.2xx isproposed.

Restrictions on HSDPA Transmission Due to Downlink Compressed Mode

The restrictions which have to be accepted for (downlink) HSDPAtransmission can be described as follows: During the gaps provided bycompressed mode, the UE (User Equipment) is free to tune to otherfrequencies and therefore cannot receive any signals on its currentlyassigned frequency.

For any given offset and for given parameters of the compressed mode, acalculation is made to determine whether HS-SCCH or HS-SDCH overlap withthe gap. Note that an overlap is already given if any single chip of theHSDPA transmission would overlap with a any single chip of the gap.Further more, because the HI transmission always fully overlaps thecorresponding HS-SCCH transmission, it is sufficient to consider onlythe latter.

Restrictions on HSDPA Transmission Due to Uplink Compressed Mode

The restrictions due to uplink compressed mode are somewhat differentfrom the downlink, because it is not the downlink HSDPA transmissionthat is causing the trouble but the uplink ACK/NACK (Acknowledge/Notacknowledge) transmission. During the gaps for uplink compressed mode,the UE is not able to transmit anything, and particularly not theACK/NACK signal. However, this does not rule out the possibility for theNode B to transmit an associated downlink HSDPA transmission before ofthe gap.

The only restriction a Node B has to take into account is the fact, thatit cannot expect the UE to transmit either ACK or NACK in response tothis HSDPA transmission. As a consequence, the Node B will not get aninformation about whether the UE has correctly received the packet anwill therefore have to retransmit the packet in any case. Under thisconfiguration the throughput can be increased: The Node B will not use aMCS (Modulation an Coding Scheme) where there is a fair chance that theUE will decode the initial transmission, but it will use a MCS where thesecond transmission has such a fair chance. Then the initialtransmission will have a rather low success probability, which means theACK/NACK signal that is lost (and is not sent) due to the uplinkcompressed mode gap is most likely a NACK signal, so the informationwould be redundant. Note that the scheduler is free to always use suchan operating point, which also has the advantage of increased timediversity due to combination of two transmissions at different times.The throughput of a higher MCS with retransmission is anyhow verysimilar to the throughput of a MCS carrying half as much payload for aninitial transmission. If this scheme is employed, uplink compressed modedoes not degrade the throughput of a HSDPA session.

This behavior may be specified in the following manner: the UE isconfigured such that it is not requested to transmit an ACK/NACK signalthat overlaps an uplink compressed mode gap. Under this configuration,not even single chip of overlap is allowed. Consequently, it will beinvisible from the outside, whether the UE could correctly decode theHSDPA transmission and therefore the UE does not even have to attempt todecode this packet, and all it has to do is store the soft decisionvalues in the virtual UE buffer where they will be combined with thenext transmission which will then be processed as usual.

Restrictions on QI Transmission Due to Uplink Compressed Mode

Similar restrictions due to uplink compressed mode for the ACK/NACKsignal also affect other uplink HSDPA transmission, i.e. the QualityIndicator (QI) transmission. Again, during the gaps for uplinkcompressed mode, the UE is not able to transmit anything, in particularalso not the QI transmission.

The QI transmission is intermittent due to the measurement feedbackcycle (even if it is possible to request the UE to transmit a QI inevery TTI as a special case). Further more the Node B has to cope withcorrupted or undecodable QI transmissions, so no special actions orprovisions are expected to be necessary for the QI transmission. It cansimply be omitted if there is a collision with an uplink compressed modegap. Again, even a single chip of overlap is not allowed.

Restrictions Due to Simultaneous Uplink and Downlink Compressed Mode

If both uplink and downlink compressed mode are activated at the sametime, or if multiple compressed mode patterns are activated, then therestrictions due to the individual gaps exist in parallel. This means adownlink or uplink transmission is only feasible, if it is compatiblewith all the gaps.

Under operation of HSDPA during compressed mode, the Node B should notschedule a HSDPA transmission for a UE which is using compressed mode,if part of the HS-SCCH information or the corresponding HS-DSCH TTIoverlaps with a gap of downlink compressed mode.

If a part of an ACK/NACK signal overlaps with a gap of uplink compressedmode, the UE is not requested to transmit it. Instead, the UE may DTXthe affected timeslot on the uplink HS-DPCCH. Furthermore the UE doesnot need to attempt to decode the transmitted packet, but is onlyrequested to store the data of the corresponding HS-DSCH TTI in thevirtual UE buffer to be able to combine them with data sent insubsequent TTIs.

The UE is also not requested to transmit a Quality Indicator signalling,if a part of it overlaps with a gap of uplink compressed mode. Insteadthe UE may DTX the affected timeslots on the uplink HS-DPCCH.

Accordingly, under the embodiments described above, an uplinktransmission (either ACK or QI) is not transmitted if it would overlapwith a gap. Furthermore, the affected transmission can also be delayeduntil a time, when it is possible to do the transmission. The delay canin principle take any value, e.g. the delayed transmission could startimmediately after the end of the gap. However, in order to ease theimplementation, it is more desirable to delay the transmission by aninteger number of timeslots.

Alternately, a delayed ACK/NACK signal may be transmitted after the gap,subsequently followed by QI transmission.

Furthermore, ACK/NACK and/or QI transmissions are sent after the gap,preferably at a time when other ACK/NACK signals or QI transmissionswould be scheduled. In this case these latter transmission are alsodelayed, until they can be sent.

Also, ACK/NACK transmission may be prioritized over QI transmission,i.e. if both an ACK/NACK signal is pending and a QI transmission thelatter is further delayed and the ACK/Nack is transmitted.

Also, only a single QI transmission is sent if a QI transmission hasbeen delayed until the nominal transmission time of a later QItransmission.

Also, a QI transmission which cannot be sent at its nominal time due toa compressed mode gap is delayed until a timeslot which is alsoallocated for QI transmission (note that normally no QI may be sentduring this particular timeslot because QI transmission is only doneintermittently).

From the perspective of a base station various embodiments focus on adata transfer method as described above, whereby a packet is sent viathe packet oriented channel, even in those cases where the correspondingreceipt cannot be sent after a first processing time because the receiptwould overlap with a transmission gap.

From the perspective of a mobile station it can be seen as a datatransfer method according as described above, whereby a packet isreceived via the packet oriented channel, even in those cases where thecorresponding receipt cannot be sent after a first processing timebecause the receipt would overlap with a transmission gap.

From the perspective of networks a communications network is proposed,that is adapted to perform a method as described above, saidcommunications network comprising at least one base station and onemobile station.

In addition, although the invention is described in connection withmobile telephones, it should be readily apparent that the invention maybe practiced with any type of communicating device, such as a personalassistant or even a PC-enabled device. It is also understood that thedevice portions and segments described in the embodiments above cansubstituted with equivalent devices to perform the disclosed methods andprocesses. Accordingly, the invention is not limited by the foregoingdescription or drawings, but is only limited by the scope of theappended claims.

REFERENCES

[1] R1-02-0492 TR 25.212 v4.3, section4.4 ‘compressed mode’ with FIG. 11

[2] R1-02-0034, Samsung, ‘Interaction between compressed mode andHSDPA’, Espoo, Finland, January 2002.

[3] R1-02-0199, TR 25.858 ‘High Speed Downlink Packet access’, Espoo,Finland, January, 2002.

[4] R1-02-0356, Secretary, ‘Revised minutes of TSG RAN WG1 #23 meeting’,Orlando, Fla., U.S.A., February 2002.

[5] R1-02-0199, TR 25.858 ‘High Speed Downlink Packet access’, Espoo,Finland, January, 2002.

The cited documents are maintained by 3 GPP, the third generationpartnership project, Address: ETSI, Mobile Competence Centre, 650, routedes Lucioles, 06921 Sophia-Antipolis Cedex and are cited in the formatused by this organisation.

1. A data transfer method, comprising: communicating data between amobile station and a base station in parallel via a packet orientedchannel and a continuous channel; communicating data packets via thepacket oriented channel; monitoring communication of data packets;detecting a transfer gap in communicated data packets; interruptingcommunication of data via the packet oriented channel and the continuouschannel when the transfer gap is detected; receiving a first datapacket; storing information obtained from the first data packet withoutsending a receipt for a first processing time; receiving a second datapacket; storing information obtained from the second data packet; andperforming a decoding making use of at least part of the information ofthe first data packet and at least part of the information of the seconddata packet.
 2. The data transfer method according to claim 1, whereinthe transfer gap is formed by an interruption of a reception at themobile station.
 3. The data transfer method according to claim 2,wherein the transfer gap is formed by an interruption of a transmissionof the mobile station.
 4. The data transfer method according to claim 1,wherein the receipt is sent after a delay.
 5. The data transfer methodaccording to claim 1, wherein the packet oriented channel is a HighSpeed Physical Downlink Shared Channel.
 6. The data transfer methodaccording to claim 3, wherein a time period for the transfer gap isdetermined by the at least one of the base station and the mobilestation.
 7. The data transfer method according to claim 1, wherein atleast one packet is sent from the base station to the mobile station viathe packet oriented channel when the at least one packet transmissiondoes not overlap with the transfer gap.
 8. The data transfer methodaccording to claim 1, wherein at least one packet is received by themobile station when the sending of the receipt overlaps with thetransfer gap.